5.7.1 Configurations
Figures 5.22 and 5.24 shows the major features of an annular combustion system comprising:
. A compressor exit diffuser to reduce the Mach number of the air before it reaches the
combustor
. Primary, secondary and tertiary injector holes through the combustor wall, these are often
plunged (rounded) to improve CD and jet positional stability. Mach number through the
holes is of the order of 0.3 to provide sufficient penetration of the jets into the combustor
. A slow moving recirculating ‘primary zone’ to enable the fuel injected to be mixed
sufficiently with the air to facilitate combustion and flame stabilisation
. A secondary zone where further air is injected and combustion is completed
. A tertiary zone where the remaining air is injected to quench the mean exit temperature to
that required for entry to the turbine, and to control the radial and circumferential
temperature traverse
. Wall cooling systems
. Fuel injectors or burners
. Ignition system